Typically, an electric saw is provided with a guard cover surrounding the upper portion of a circular saw blade. In most cases, a dust collecting case is arranged either on the side of the guard cover or at the rear thereof.
With the configuration in which the dust collecting case is arranged on the side of the guard cover, not only is it easy to increase the size of the dust collecting case but also it is possible to realize a high recovery rate of chips using the upward chip-hurling force exerted by the tips of teeth of the rotating circular saw blade. However, the dust collecting case becomes an obstacle in a cutting work, thereby reducing the workability. Another problem is that the dust collecting case makes it difficult to observe the cutting spot. In view of this, JP5-31701A discloses a configuration in which a dust collecting case is made transparent, with its frontal lower portion cut away, in an effort to increase the visibility of a cutting spot. However, this configuration fails to avoid the reduction in workability caused by the dust collecting case arranged on the side of a guard cover.
On the other hand, the configuration with which the dust collecting case is arranged at the rear of the guard cover provides advantages in that it is compact, easy to perform a task while allowing a user to readily observe the cutting spot of an electric saw. However, this configuration increases the distance between the cutting spot and the dust collecting case, which in turn reduces the recovery rate of chips. Another drawback is that the passage of the dust collecting case tends to be filled with chips.
Taking this into account, Japanese Patent Laid-open Publication No. 6-335904 discloses a configuration with which a pipe is inserted through a guard cover from the front portion of the latter. The tip end of the pipe is arranged adjacent to a cutting spot, thus forming a passage through which to introduce chips into a dust collecting case. In other words, with this rear arrangement type construction, the chips drawn into the guard cover are collected in the dust collecting case by use of the air stream generated within the guard cover during rotation of a circular saw blade. In addition to the air stream, the upward chip-hurling force exerted by the tips of teeth of the circular saw blade may be used in this construction. As a result, it is possible to further increase the recovery rate of chips.
However, if the passage through which the chips are delivered to the dust collecting case becomes longer, the interior of the passage tends to be full of the chips. Although it becomes possible to use the upward chip-hurling force by arranging the tip end of the passage adjacent to the cutting spot, this reduces the air stream introduced into the passage. As a result, the passage has an increased tendency to be clogged by the chips. It is the conventional practice that, when the passage is clogged, the cutting work is stopped for a while to dismantle and clean the electric saw. This poses a problem in that the dismantling and cleaning operation is onerous and highly time-consuming. During the cleaning operation, care should be taken in terms of safety, e.g., not to touch the circular saw blade. This also leaves a room for improvement.